The Mightiest Flow on Earth: Understanding the Antarctic Circumpolar Current

In the wild Southern Ocean, beneath the crashing waves and circling albatrosses, a hidden force moves with unmatched power — encircling an entire continent, linking oceans, and shaping the planet’s climate. This is the Antarctic Circumpolar Current (ACC), the largest and most influential ocean current on Earth.

It may not be visible to the eye, but without it, Antarctica would be warmer, sea levels would be higher, and the global climate as we know it wouldn’t exist.

What Is the Antarctic Circumpolar Current?

The Antarctic Circumpolar Current is a massive band of water that flows continuously from west to east around Antarctica. It’s the only ocean current that makes a complete loop around the globe without being blocked by land — spinning through the Southern Ocean like a vast planetary conveyor belt.

Stretching more than 20,000 kilometers in circumference and reaching depths of over 4,000 meters in places, the ACC transports an estimated 130 million cubic meters of water per second — that’s more than 100 times the flow of all the world’s rivers combined.

Why Does It Exist?

The ACC is driven by strong westerly winds and the unique configuration of the Southern Hemisphere. Antarctica is surrounded by open ocean, with no continents interrupting the flow — unlike the Arctic, which is enclosed by landmasses. This gives the current a clear path to circle the globe, powered by the Earth's rotation and the pressure gradient between different water masses.

But the ACC isn’t just a ribbon of water moving in circles. It’s a dynamic system that connects the Atlantic, Pacific, and Indian Oceans, redistributing heat, carbon, and nutrients across the planet.

A Climate Regulator on a Global Scale

The Antarctic Circumpolar Current plays a critical role in regulating Earth’s climate. Acting like a thermal barrier, it isolates Antarctica from warmer northern waters, helping to keep the continent frozen — which in turn helps regulate global sea levels.

The ACC also facilitates the global thermohaline circulation, often referred to as the “global ocean conveyor belt.” By mixing deep, cold waters from the Southern Ocean with warmer surface currents, it helps drive the movement of heat and carbon dioxide between oceans and the atmosphere.

This mixing process is vital for the health of the planet. It sequesters vast amounts of carbon dioxide in deep waters and supports rich marine ecosystems by upwelling nutrients from the ocean depths — feeding krill, whales, and seabirds alike.

A Force You Can Feel

For those who travel to Antarctica by ship — particularly across the notorious Drake Passage — the ACC is more than a scientific concept. It’s a physical presence. The rolling swells, the powerful winds, the unpredictable seas — all are shaped by the restless motion of this great current.

Many guests ask why the Drake can be so rough. The answer lies in part with the ACC. The combination of powerful winds and an uninterrupted flow of water creates conditions that can be challenging — but also thrilling for those seeking real adventure.

Changing Waters, Changing World

Like many systems on our planet, the Antarctic Circumpolar Current is under pressure from climate change. Warming oceans are altering the temperature and salinity of water masses, which may affect the speed and behavior of the ACC.

These changes matter far beyond Antarctica. Shifts in the ACC can influence weather patterns in South America, Australia, and beyond — and even impact global heat distribution and the rate of ice sheet melting.

Scientists continue to monitor the current using satellite data, underwater floats, and research vessels — many of which operate in the very waters our expeditions traverse.

Why It Matters to Us

At Terra Nova Expeditions, we don’t just sail through the Southern Ocean — we share its stories. The Antarctic Circumpolar Current may be invisible, but it’s one of the most powerful forces shaping the environment we explore.

Understanding the ACC gives our guests a deeper appreciation for the interconnectedness of Earth’s systems — and the vital role Antarctica plays in the health of the entire planet.

So the next time you feel the roll of the Southern Ocean beneath your feet, know that you’re riding the mightiest current on Earth.